[PATCH linux dev-4.10 1/2] drivers/iio: dps310 Temperature measurement fix.

[Christopher Bostic]

On 7/24/17 8:41 PM, Joel Stanley wrote:
> On Tue, Jul 25, 2017 at 6:55 AM, Christopher Bostic
> <cbostic at linux.vnet.ibm.com> wrote:
>> Add a manufacturer's suggested workaround to deal with early revisions
>> of chip that don't indicate correct temperature.  Readings can be in the
>> ~60C range when they should be in the ~20's.
>>
>> Signed-off-by: Christopher Bostic <cbostic at linux.vnet.ibm.com>
> Looks okay Chris. Has there been an errata issued for the device so I
> can check what we're doing here?

I wasn't able to find any official documentation from the manufacturer 
on this.  This is based on existing FSP workarounds for this device.

Thanks,
Chris
>
> I don't think there's much value in the #defines without meaningful
> labels, so I removed them when applying the patch.
>
> Cheers,
>
> Joel
>
>> ---
>>   drivers/iio/pressure/dps310.c | 49 ++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 48 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/iio/pressure/dps310.c b/drivers/iio/pressure/dps310.c
>> index 1b54ae0..f351c26 100644
>> --- a/drivers/iio/pressure/dps310.c
>> +++ b/drivers/iio/pressure/dps310.c
>> @@ -56,7 +56,12 @@
>>   #define  DPS310_FIFO_EN                BIT(5)
>>   #define  DPS310_SPI_EN         BIT(6)
>>   #define DPS310_RESET           0x0c
>> +#define DPS310_TEMP_FIX_E      0x0e
>> +#define DPS310_TEMP_FIX_F      0x0f
>>   #define  DPS310_RESET_MAGIC    (BIT(0) | BIT(3))
>> +#define DPS310_TEMP_FIX_32     0x32
>> +#define  DPS310_TEMP_ERR_FIXED BIT(1)
>> +#define DPS310_TEMP_FIX_62     0x62
>>   #define DPS310_COEF_BASE       0x10
>>
>>   #define DPS310_PRS_BASE                DPS310_PRS_B0
>> @@ -219,6 +224,9 @@ static bool dps310_is_writeable_reg(struct device *dev, unsigned int reg)
>>          case DPS310_MEAS_CFG:
>>          case DPS310_CFG_REG:
>>          case DPS310_RESET:
>> +       case DPS310_TEMP_FIX_E:
>> +       case DPS310_TEMP_FIX_F:
>> +       case DPS310_TEMP_FIX_62:
>>                  return true;
>>          default:
>>                  return false;
>> @@ -308,7 +316,7 @@ static int dps310_read_raw(struct iio_dev *iio,
>>          .writeable_reg = dps310_is_writeable_reg,
>>          .volatile_reg = dps310_is_volatile_reg,
>>          .cache_type = REGCACHE_RBTREE,
>> -       .max_register = 0x29,
>> +       .max_register = 0x62,
>>   };
>>
>>   static const struct iio_info dps310_info = {
>> @@ -317,6 +325,41 @@ static int dps310_read_raw(struct iio_dev *iio,
>>          .write_raw = dps310_write_raw,
>>   };
>>
>> +/*
>> + * Some verions of chip will read temperatures in the ~60C range when
>> + * its acutally ~20C. This is the manufacturer recommended workaround
>> + * to correct the issue.
>> + */
>> +static int dps310_temp_workaround(struct dps310_data *data)
>> +{
>> +       int r, reg;
>> +
>> +       r = regmap_read(data->regmap, DPS310_TEMP_FIX_32, &reg);
>> +       if (r < 0)
>> +               return r;
>> +
>> +       if (!(reg & DPS310_TEMP_ERR_FIXED)) {
>> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0xA5);
>> +               if (r < 0)
>> +                       return r;
>> +
>> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x96);
>> +               if (r < 0)
>> +                       return r;
>> +
>> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_62, 0x02);
>> +               if (r < 0)
>> +                       return r;
>> +
>> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_E, 0x00);
>> +               if (r < 0)
>> +                       return r;
>> +
>> +               r = regmap_write(data->regmap, DPS310_TEMP_FIX_F, 0x00);
>> +       }
>> +       return r;
>> +}
>> +
>>   static int dps310_probe(struct i2c_client *client,
>>                          const struct i2c_device_id *id)
>>   {
>> @@ -379,6 +422,10 @@ static int dps310_probe(struct i2c_client *client,
>>          if (r < 0)
>>                  return r;
>>
>> +       r = dps310_temp_workaround(data);
>> +       if (r < 0)
>> +               return r;
>> +
>>          r = devm_iio_device_register(&client->dev, iio);
>>          if (r)
>>                  return r;
>> --
>> 1.8.2.2
>>